Medical telemetry system

ABSTRACT

Disclosed is a medical telemetry system for collecting vital data, specifically body temperature, the system consisting of a plurality of measuring sensors  10  and a collecting device  30 . Each sensor  10  is placed at a predetermined location of the patient&#39;s body and automatically detects the vital data value to be measured. Upon a measurement termination signal, which is preferably acoustical, the sensor can be removed from the measuring location and stored away. For a defined period of time, e.g. two hours, the sensor  10  remains in an active state in which it transmits the detected measured value upon request. The measured value along with an ID code and status signals, which relating for instance to the battery voltage, can be interrogated and stored by means of a collecting device  30 . Upon expiry of the defined period of time, the measured value is cleared, and the sensor  10  is automatically reset to an energy-saving rest condition.

DESCRIPTION

Three types of apparatus are nowadays in use for taking routinemeasurements of human temperature in hospitals: analogous, electronicand infrared clinical thermometers.

The conventional analogous liquid-glass clinical thermometers operate onthe basis of the temperature-dependent expansion of a liquid metal,specifically mercury. Measurements may be taken in the axilla, mouth orrectum. Reading the measured temperature value and resetting thethermometer by shaking the thermometer is usually done by medicalpersonnel. These thermometers are inexpensive, and, due to the glassbody, may be disinfected without problem. Disadvantages, however, residein the fragility of the body, in the relative poor readability of themeasurement results, and in the frequency such thermometers are stolenby patients and clinical personnel.

Compact electronic clinical thermometers operate on the basis of thetemperature-dependent change of resistance of a thermistor. Thesethermometers have a body of plastics material. These thermometers alsopermit measurements to be taken in the axilla, mouth or rectum. Prior totaking a measurement, the medical personnel is required, for hygienicreasons, to provide thermometers of this type with a cover. This causesadditional cost and produces special refuse. The thermometers are almostunbreakable, well readable and only little more expensive than analogousclinical thermometers. However, they also are frequently stolen.

Infrared clinical thermometers measure the temperature-dependentradiation of the tympanic membrane. They operate fast but are availablefor measurements in the ear only, and the medical interpretation of themeasurement result is not always without problem. Again, hygienicconsiderations require these thermometers to be provided with a freshprotective cover prior to every measurement. Placing the thermometer atthe measurement location requires trained personnel and may, in case ofrepeated measurements, cause injure and pain. Clinical thermometers ofthis type are less suited for private use and, as a consequence, are notstolen. They are, however, substantially more expensive than analogousand electronic clinical thermometers.

Specific methods of electronically measuring the body temperatureinvolve telemetric systems, such as are known from DE 3 219 558 A1, DE 4441 083 C1, U.S. Pat. No. 4,503,862, and U.S. Pat. No. 4,865,044. Thesesystems include a measuring probe (the thermometer proper) to bedisposed on or in the patient and a separate evaluation unit.

In the system of DE 3 219 558 A1, a micro probe is implanted in the bodyand supplied with energy for the measurement by means of a highfrequency field. The transmission of the measured value is done byabsorption modulation of the HF field. Due to the small size of themeasuring probe, it is difficult to supply the probe with the energyrequired for the measurement and for the transmission of the measuredvalue. It is therefore necessary to expose the patient to a very strongelectromagnetic field. The measuring probe is switched on and off byturning on and off the HF field. Measured values can be transmitted onlywhen the probe is on the patient. The system is unsuited for routinemeasurements in a hospital.

In the system according to DE 4 441 083 C1, a telemetric measuring probeis included in an adhesive plaster which is placed on the desiredlocation of the patient's skin. In addition to the fact that this typeof placement is unsuited for measuring body temperatures at the usuallocations, the patient's skin is unnecessarily irritated by the possiblyrepeated application and removal of plasters as would be required fortaking routine measurements. Also, undesired special refuse is produced.Further, changing the plaster involves work for the nursing personnel.The provision of a largesize antenna in the form of a pillow to beplaced under the patient, as recommended in this document, is expensiveand hardly practical for hygienic reasons. Also, the measuring probeoperates in this system only within a high frequency field and yieldsmeaningful measurement results only if the probe is placed on thepatient.

U.S. Pat. No. 4,503,862 describes a system in accordance with the firstpart of claim 1, wherein each patient is given his own battery-poweredmeasuring sensor. On her round, the nurse carries a receiver unit fromone patient to the next and actuates the transmitter of the respectivesensor next to the receiver unit to transmit the detected temperaturevalue. This process must be repeated for every individual. patient. As adisadvantage of this system, the sensor produces correct measurementresults only if placed on the patient. The detected data must beallocated to the individual patients manually, e.g. by means of alisting.

The temperature monitoring system proposed in U.S. Pat. No. 4,865,044uses a plurality of telemetric sensors. When a predetermined thresholdvalue is exceeded, these sensors transmit continuously and inpredetermined intervals their identification number and a modulatedsignal which corresponds to the measured temperature. As a disadvantage,once the starting condition has been reached, the sensors transmitcontinuously irrespective of whether the receiver unit is turned on andwhether the sensors are within the range of the receiver unit. To saveenergy, it has been proposed to turn on and off the sensorsperiodically. When the period is relatively short, updated measurementvalues may be obtained virtually continuously, but this results in ahigh energy consumption. A long period reduces the energy consumption,but the waiting time until the moment the next actual measurement valueis received may become relatively long. Since no provision is made tocollect the detected temperature data selectively, the system isunsuited for routine temperature measurements in hospitals.

It is a general object of the invention to provide a medical telemetrysystem for vital data, specifically for taking routine measurements ofthe body temperature, which system avoids the disadvantages of the priorart explained above. A more specific object may be considered to residein permitting measurement of the body temperature at the usualmeasurement locations at low expenses, (i.e. low cost per measurement),minimum labor for the nursing personnel, maximum safety of the data, andhigh comfort for the patient.

This object is met by the medical telemetry system set forth in claim 1.In the system according to the invention, the individual measuringsensors continuously and automatically monitor a predetermined thresholdvalue and start a measurement when this threshold value is exceeded. Themeasured value is stored in the sensor and transmitted upon request froma collecting device.

When admitted to a hospital, every patient is given his own measuringsensor. Within an agreed period of time, the patients place theirpersonal measuring sensor at the intended measuring location. When themeasurement has been taken, the patient can remove the measuring sensorfrom the measuring location and store it in a holder provided for thispurpose. Even after the measurement, the sensor remains active over adefined period of time during which it stores the measured value andtransmits it upon receipt of a request signal. Nursing personnel isrequired only for collecting the measurement values stored in themeasuring sensors, which is done by means of a collecting device thatneeds to be taken only close to the individual measuring sensors inorder to collect the measured value telemetrically upon transmission ofthe request signal. There is thus no need to touch either the patient orthe sensor, which is of advantage particularly in case of highlycontagious diseases. Moreover, it is not at all necessary for thepatient to be present at the time the measured value is collected. Sincethe measuring sensor has no display of its own, it is useless as ameasuring device for private purposes, which should have a greatinfluence on the disappearance of thermometers in hospitals.

The embodiment of claim 2 is useful because the patient does not have toplace the measuring sensor into operation, and there is the additionaladvantage that no mechanical keys or switches with correspondingopenings in the sensor body are required. This improves especially thehygienic properties of the sensor body.

The embodiment of claim 3 realises a maximum thermometer system as iscommon for routine temperature measurements.

The embodiment provided in accordance with claim 4 offers high comfortfor the patient who needs to leave the measuring sensor at the measuringlocation for only a minimum period of time.

The feature of claim 5 can be useful in that measured values can beevaluated in minimum time.

The ID code of claim 6 which is transmitted along with the data ensuresa unique and unambiguous association of the measurement results receivedby the collecting device to the individual patients.

In accordance with claim 7, since the values, which are not collectedwithin a predetermined period of time, are cleared, confusion between“old” and “new” measured values is safely excluded. In accordance withclaim 8, the erasing can be done immediately upon the transmission ofthe respective measured value.

The embodiment of the invention in accordance with claim 9 has theadvantage that the outer appearance of the measuring sensor correspondsto that of a conventional clinical thermometer so that the patients haveno difficulty to take their own measurements as usual. At the same time,the thermometer body is suited for receiving a sufficiently powerfulbattery and powerful antenna, which is of advantage for the signaltransmission.

The development of the invention set forth in claim 10, according towhich the sensor is shaped so that the sensor body can be sterilisedwhen changing the patient, improves the hygienic aspect when takenroutine measurements of the body temperature in a hospital.

Claims 11 and 12 relate to the possibility of transmitting anddisplaying, on the collecting device, information concerning thecondition of the individual sensors in addition to the measured valuesproper. This information chiefly includes the charging condition of thebattery. When the voltage drops below a critical value, the user isgiven information that the battery must be changed. In addition to thisstatus information, it is possible to transmit, e.g., a reference countcharacteristic of the overall function of the measuring sensor. If thiscount changes towards values outside a range defined as normal,malfunction of the device may be displayed in any suitable way, e.g. ona display of the collecting device.

The further developments of the invention set forth in claims 13 to 15result in further reduced labor for the nursing personnel.

Preferred embodiments of the invention will now be explained withreference to the drawing. In the drawing,

FIG. 1 shows a sensor,

FIG. 2 shows a collecting unit for use in connection with sensors inaccordance with FIG. 1, and

FIG. 3 shows a modification of the overall telemetry system.

The sensor 10 shown schematically in FIG. 1 has a body 11 the outershape of which corresponds to that of a traditional liquid-glassclinical thermometer or compact electronic clinical thermometer. Thebody 11 is entirely sealed externally and is made of a syntheticmaterial which permits disinfection or sterilisation.

A temperature sensitive measuring element 12, e.g. a thermistor, isdisposed at the end of a narrower part of the body 11, the overall shapeof which is somewhat rod-like.

The larger-diameter portion of the body 11 includes an electronicmeasurement and control circuit 13, a battery 14, an antenna 15, amemory 16 and a, preferably acoustic, signalling device 17. Thecomponents 13 to 17 are disposed on a common circuit board 18 mountedinside the body 11. The measuring element 12 is connected to themeasurement and control circuit 13 by means of connecting wires 19.Further connecting lines between the components 13 to 17 are provided onthe circuit board 18 but now shown in the drawing.

In FIG. 1, the antenna 15 is shown merely schematically as an areataking up part of the circuit board 18. In a practical embodiment, theantenna 15 may extend in one or a plurality of loops around the entireouter periphery of the circuit board 18 to increase the effectivesurface of the antenna.

The collecting device 30 schematically shown in FIG. 2 includes aprocessor 31, a display 32, e.g. of the liquid crystal type, an antenna33, a keyboard 34 and external terminals 35.

In practical use, each patient is given his own sensor 10 when admittedto the hospital. The nursing personnel records, in a listing or in anyother suitable manner, the association between the patient and the IDcode of the sensor. At predetermined times, e.g. between 8 and 9 a.m. orupon request by the nursing personnel, the sensor 10 is placed at thepredetermined measuring location. Most patients would be in a positionto do this themselves. No turn-on or control operations are necessary.The presence of nursing personnel is unnecessary also during thewarming-up phase of the measuring element.

The sensors 10 continuously monitor a fixed threshold value (e.g. 32° C.in case of measuring body temperatures) and automatically start theactual measurement when this value is exceeded.

Upon termination of the measurement, which is signalled acoustically bythe signalling device 17, the patient may remove the sensor 10 from themeasuring location and store it in a prepared holder until the nextmeasurement is taken. No intermediate manipulation is required, such asshaking down the mercury column of conventional medical thermometers.

At any desired time within a wide time window (e.g. two hours) after thestart of the measurement, a nurse will take the collecting device 30near the patient's sensor 10 at a distance of 1 to 2 meters. Byactuation of a CALL key on the keyboard 34, a request signal istransmitted from the antenna 33 of the collecting device 30 to themeasurement and the control circuit 13 of the sensor 10, which thereupontransmits the value measured by the measuring element 12 via the antenna15.

At the same time, an ID code, which is stored in the memory 16 of thesensor 10, is transmitted. The measured value is thus automaticallylinked to an identification of the transmitting sensor 10 and thus tothe respective patient. The measured value is displayed in connectionwith the ID code on the display 32 of the collecting device 30.

Prior to, or simultaneously with, the transmission of the measured valuefrom the sensor 10 to the collecting device 30, one or a plurality ofstatus signals are transmitted which are representative of the functionof the sensor 10, particularly the charging condition of the battery 14.The display 32 of the collecting device 30 will display a message, e.g.“ERROR” in case the sensor 10 is out of order, and e.g. “LOW BAT” incase of insufficient battery voltage.

If required, the measured value, ID code and status signals may befurther transmitted via the terminals 35 or via another wirelesstransmitting channel to a PC, a printer, a further collecting unit 30,or a remote reading device.

Collecting the measured value of an entire hospital section using thecollecting device 30 occupies the nursing personnel only a few minutes.All measured values are unmistakably stored by their linking to the IDcode of the sensors 10 and can be entered by the nursing personnel intopatients' files at any time of the working day.

To this end, the personnel selects the various data records by operatingthe UP and DOWN keys on the keyboard 34 of the collecting device 30.When all data have been transferred, the entire measured-value memory ofthe collecting device 30 is cleared by pressing the CLEAR key. Thisinsures that in each round only those measured values which haveactually been interrogated, are stored in the collecting device 30.Sensors 10 which are missing, are out of order or have not beeninterrogated, are not entered in the record list of the collectingdevice 30.

When the patient is dismissed from the hospital, the sensor 10 iscollected and disinfected or sterilised and thus prepared for subsequentuse. Infections by contaminated sensors are thereby safely excluded.

Synthetic thermometer covers, which are nowadays widely used to avoidcross-contamination, are rendered superfluous with the medical telemetrysystem of the present invention, thus avoiding special refuse inaddition to involving a considerable cost advantage. Moreover, thesensor is unattractive for both patients and nurses, so that theftshould be infrequent.

In the development schematically shown in FIG. 3, an intermediatestation 40 is installed in the patients' room. At given times, thepatients are requested by an optical and/or acoustical signal via theintermediate station 14 to place their sensors 10. Upon termination ofthe measuring process, the intermediate station 40 automaticallyinterrogates the measured values along with the ID codes and statussignals and transmits them to a central collecting device 30.

What is claimed is:
 1. A medical telemetry system for collecting vitaldata including patients' body temperatures, the system comprising aplurality of measuring sensors and collecting device, each said sensorincluding: measuring means for performing measurement cycles to detectvalues of vital data; memory means for storing the value detected in thelast measurement cycle performed by said measuring means; means fortransmitting the last detected value in response to a request signalreceived from said collecting device; clearing means for automaticallyremoving the stored value from said memory means, and; means forcontinuously supervising a threshold value and starting a measurementcycle when said threshold value is exceeded.
 2. The telemetry of claim1, wherein the sensor includes means for terminating the measurementcycle when the gradient of change of the value detected by saidmeasuring means falls below a predetermined value.
 3. The telemetrysystem of claim 2, wherein said sensor includes means for producing ameasurement cycle termination signal perceptible by the patient.
 4. Thetelemetry system of claim 2, wherein said sensor includes means fortransmitting a measurement cycle termination signal to said collectingdevice.
 5. The telemetry system of claim 1, wherein said memory meansfurther holds an ID code of said sensor and said transmitting means isadapted to transmit said ID code along with said detected value.
 6. Amedical telemetry system for collecting vital data including patients'body temperatures, the system comprising a plurality of measuringsensors and collecting device, each said sensor including: measuringmeans for performing measurement cycles to detect values of vital data;memory means for storing the value detected in the last measurementcycle performed by said measuring means; means for transmitting the lastdetected value in response to a request signal received from saidcollecting device; clearing means for automatically removing the storedvalue from said memory means, and; means for actuating said clearingmeans upon expiry of a predetermined period of time following ameasurement cycle.
 7. A medical telemetry system for collecting vitaldata including patients' body temperatures, the system comprising aplurality of measuring sensors and collecting device, each said sensorincluding: measuring means for performing measurement cycles to detectvalues of vital data; memory means for storing the value detected in thelast measurement cycle performed by said measuring means; means fortransmitting the last detected value in response to a request signalreceived from said collecting device; clearing means for automaticallyremoving the stored value from said memory means, and; means foractuating said clearing means upon transmission of said last detectedvalue.
 8. A medical telemetry system for collecting vital data includingpatients' body temperatures, the system comprising a plurality ofmeasuring sensors and collecting device, each said sensor including:measuring means for performing measurement cycles to detect values ofvital data; memory means for storing the value detected in the lastmeasurement cycle performed by said measuring means; means fortransmitting the last detected value in response to a request signalreceived from said collecting device; and clearing means forautomatically removing the stored value from said memory means, whereinat least one sensor comprises an elongated sensor body resembling thebody of a conventional clinical thermometer.
 9. The telemetry system ofclaim 8, wherein said sensor body is sterilizable.
 10. The telemetrysystem of claim 5, wherein said sensor includes means for producing astatus signal indicative of a function of the sensor.
 11. The telemetrysystem of claim 10, wherein said collecting device includes means forvisually displaying the detected value, said ID code and said statussignal of a transmitting sensor.
 12. A medical telemetry system forcollecting vital data including patients' body temperatures, the systemcomprising a plurality of measuring sensors and collecting device, eachsaid sensor including: measuring means for performing measurement cyclesto detect values of vital data; memory means for storing the valuedetected in the last measurement cycle performed by said measuringmeans; means for transmitting the last detected value in response to arequest signal received from said collecting device; clearing means forautomatically removing the stored value from said memory means, and; thetelemetry system further including an intermediate station disposedwithin a range of transmission of said plurality of sensors for relayingthe signals transmitted by each sensor to said collecting device. 13.The telemetry system of claim 12, wherein said intermediate stationincludes means for producing a measurement request signal perceptible bythe patients.
 14. The telemetry system of claim 12, wherein saidintermediate station includes means for transmitting a clearing signalto actuate the clearing means of a sensor upon receipt of the detectedvalue from said sensor.